Normally, the inlet and outlet pipe openings of a pneumatic pressure valve are commonly used on general industrial equipment which is usually provided with screw threaded types of connections which simplifies the connection structure and reduces the overall cost. In other words, the input and output ports are provided with pipe thread openings which are connected to the fluid conveying piping.
On the other hand, a pneumatic pressure valve which is installed on a railroad car is connected to a pipe bracket which is usually a perforated block on which the pneumatic valves and piping to perform the required control functions of applying and releasing the air brakes. In practice, there are passageways which are equivalent to piping connections between the threaded openings of the metal pipe bracket and the valves. Usually, a flange is provided on one side of the pneumatic valve for connection purposes. In other words, the flange portion of the valve is provided with the inlet and outlet ports so that it is connected and fixed in alignment with the connection holes of the pipe bracket which are tightly sealed by rubber O-rings, gaskets, and the like. That is the pneumatic valve which is to be installed on the pipe bracket has an apertured flange. The flange portion is generally manufactured as an integral part of the valve body which is made by a casting process.
The main reason for mounting the pneumatic pressure valves used for the air brake control system of railroad vehicles on the multiple port pipe bracket is to be able to accommodate a number of different operating valves. In other words, the use of a pipe bracket allows the amount of the piping or tubing to dramatically be reduced while at the same time each of the different types of fluid pressure valves can be easily removed and replaced during normal maintenance and inspection periods.
However, the various types of pneumatic pressure valves to be installed in the air brake control system of a railroad car must be all manufactured with the same flange portion to match the pipe bracket. In addition, the mass produced pneumatic valves having the exact pipe connecting openings are expensive since the requisite reproduction is not always feasible. Therefore, the pneumatic valves having a flange type of interconnections generally must be produced in relatively small quantities. A separate casting mold must be made for each different valve. This results in reduced productivity and increased costs which is a competitive disadvantage. In other words, the valves cannot be simply mounted on the pipe bracket because of the required piping openings so that the main valve body must be changed to a flange type of device. Thus, the pneumatic valve must be a special type which means that it is expensive to make and produce. In addition, in order to produce a casted valve with a flange, it is necessary to use various core members in conjunction with the mold to form the required passageways so that such an operation is a very tedious and relatively expensive process.